A method for efficiently degrading plant straw using a microbial composite preparation

Abstract

The invention relates to the technical field of straw degradation, and discloses a method for efficiently degrading plant straw by using a microbial composite preparation. The method comprises the following steps: adding urea to a sodium hydroxide solution and stirring evenly, adding straw powder, performing ultrasonic treatment at 60-70 DEG C, adding calcium chloride and continuing ultrasonic treatment, reducing the temperature to -30--50 DEG C, keeping the temperature for 10-30 min, heating the temperature to 50-60 DEG C and stirring, reducing the temperature to room temperature, and performing vacuum drying to obtain pre-treated straw powder A; adding the pre-treated straw powder A to a dilute sulfuric acid solution, stirring at 40-60 DEG C, cooling to room temperature, and freeze drying to obtain pre-treated straw powder B; adding lanthanum chloride to water, stirring at 40-60 DEG C for 10-20 min, adding ε-polylysine and aspartic acid thereto under stirring, adding a composite enzyme and stirring evenly to obtain a composite enzyme liquid; mixing the pre-treated straw powder B and the composite enzyme liquid evenly, adding the mixture to an acetic acid-sodium acetate buffer solution and mixing evenly, performing enzymolysis for 72-96 h, and performing centrifugation.

Description

Technical Field

[0001] The invention relates to the technical field of straw degradation, and in particular to a method for efficiently degrading plant straw by utilizing a microbial composite preparation. Background Art

[0002] The mining and use of mineral fuels have caused serious environmental pollution, and the reserves are limited. Biomass plays a connecting role in the green carbon science framework. From the current research hotspots and frontiers, as well as the application status and development prospects, in order to promote the sustainable development of the national economy, it is very necessary to develop biomass energy and produce renewable bioenergy hydrogen and fuel alcohol.

[0003] Straw is an important agricultural waste. As a type of renewable resource, it is mainly composed of cellulose, hemicellulose, lignin, and a small amount of fat, protein, ash, etc. Its composition varies depending on the type of plant, but the largest content is cellulose, which has a high utilization value.

[0004] Agricultural residues such as straw are the most promising cellulose reservoirs. If these lignocellulosic polysaccharides are degraded into monosaccharides, it is expected that straw biomass can be eventually converted into fuel alcohol or hydrogen through fermentation, opening up a new way to produce renewable bioenergy.

[0005] The saccharification and degradation of straw cellulose is the first step in converting agricultural waste into bioenergy fuel alcohol or hydrogen, and it is also the key step restricting the bioenergy of straw. Improving the degradation and saccharification efficiency of straw cellulose is the goal pursued by scientists. In recent years, domestic and foreign researchers have done a lot of research on improving the efficiency of enzyme degradation of lignocellulose, mainly focusing on the following aspects:

[0006] 1. Screening highly efficient lignocellulose-degrading bacteria or obtaining new highly efficient degradation strains through genetic engineering recombination;

[0007] 2. Study on the influence of different production processes on the enzyme production efficiency of strains;

[0008] 3. Pre-treat the straw by physical or chemical methods to improve degradation efficiency;

[0009] 4. Analyze the composition of different plant lignocellulose and its effect on saccharification efficiency;

[0010] 5. Some preliminary studies were conducted on the inhibitory factors of enzymatic hydrolysis.

[0011] However, the existing technology has not yet achieved a satisfactory level in terms of saccharification efficiency of wood cellulose. First, the activity of most enzymes decreases significantly when degrading straw-based natural cellulose. Second, the target product of straw cellulose degradation and saccharification is monosaccharide, but during the enzymatic reaction, monosaccharide will continue to hydrolyze to generate non-target products such as organic acids, thereby reducing the sugar production efficiency.

[0012] In terms of the structural composition of straw, as long as the rate-limiting step of degrading cellulose into monosaccharides is broken through, biomass energy fuel alcohol or hydrogen can be produced through fermentation. In theory, straw waste can be turned into a treasure trove of renewable biological resources.

[0013] At present, how to obtain higher straw cellulose degradation efficiency and improve the efficiency of straw degradation into monosaccharides during the saccharification process of straw-based biomass is of great significance, laying a solid foundation and theoretical basis for the efficient degradation of biomass cellulose to produce clean energy such as fuel ethanol and hydrogen. Summary of the invention

[0014] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for efficiently degrading plant straw using a microbial composite preparation.

[0015] A method for efficiently degrading plant straw using a microbial composite preparation comprises the following steps:

[0016] S1, drying plant straw, crushing and sieving to obtain straw powder;

[0017] S2, adding urea to sodium hydroxide solution and stirring evenly, adding straw powder thereto, ultrasonically treating at 60-70°C for 1-2h, adding calcium chloride and continuing ultrasonically treating for 10-30min, cooling to -30--50°C, keeping warm for 10-30min, heating to 50-60°C and stirring for 10-20min, cooling to room temperature, filtering, washing, and vacuum drying to obtain pretreated straw powder A;

[0018] S3, adding the pretreated straw powder A to a dilute sulfuric acid solution, stirring at 40-60° C. for 1-2 h, cooling to room temperature, filtering, washing, and freeze-drying to obtain pretreated straw powder B;

[0019] S4, adding lanthanum chloride to water, stirring at 40-60° C. for 10-20 min, adding ε-polylysine and aspartic acid thereto under stirring, stirring for 1-4 h, adding complex enzyme thereto and stirring evenly to obtain complex enzyme solution;

[0020] S5. Mix the pretreated straw powder B and the complex enzyme solution evenly, add them into the acetic acid-sodium acetate buffer solution and mix evenly, place them on a shaker at 40-46°C for enzymolysis for 72-96 hours, and centrifuge.

[0021] Preferably, in S1, the plant straw is at least one of sorghum straw, corn straw, wheat straw and rice straw.

[0022] Preferably, in S1, the moisture content of the straw powder is ≤5%.

[0023] Preferably, in S2, the mass ratio of urea, straw powder and calcium chloride is 1-3:10-20:0.1-0.5.

[0024] Preferably, in S2, the ultrasonic frequency is 10-16 kHz.

[0025] Preferably, in S2, the concentration of the sodium hydroxide solution is 0.5-1.5 mol / L.

[0026] Preferably, in S3, the mass fraction of the dilute sulfuric acid solution is 1-2%.

[0027] Preferably, in S3, deionized water is used for washing 1-3 times.

[0028] Preferably, in S4, the mass ratio of lanthanum chloride, ε-polylysine, aspartic acid and complex enzyme is 0.001-0.01:1-10:0.1-1:1-2.

[0029] Preferably, in S4, the complex enzyme comprises cellulase, xylanase, cellobiase and pectinase.

[0030] Preferably, per gram of the complex enzyme, the enzymatic activity of cellulase is 3000-5000U, the enzymatic activity of xylanase is 2000-4000U, the enzymatic activity of cellobiase is 4000-6000U, and the enzymatic activity of pectinase is 5000-6000U.

[0031] Preferably, in S5, the mass ratio of the pretreated straw powder B to the complex enzyme solution is 10-20:3-6.

[0032] Beneficial effects:

[0033] The present invention adds straw powder to a sodium hydroxide solution, which can effectively weaken the binding force between lignin molecules under the synergistic effect of urea, cooperate with calcium chloride to combine with lignin, and cooperate with high and low temperature treatment on the basis of ensuring the stability of the cellulose structure to quickly remove lignin.

[0034] The pretreated straw powder A has a large number of pores and wrinkled structures. On the one hand, it is more conducive to the entry of acid at 40-60°C, which promotes the hydrolysis of fiber into hemicellulose, so that it can be degraded at a lower temperature and is not easy to generate by-products such as furoic acid. On the other hand, its developed pore structure is more conducive to increasing the contact area between the subsequent complex enzyme and cellulose or hemicellulose, greatly improving the cellulose degradation efficiency and significantly increasing the monosaccharide yield.

[0035] The present invention causes the structure of lignin to be completely broken, which not only greatly reduces the adsorption of lignin to the complex enzyme, but also reduces the resistance of lignin to the enzyme. The present invention adopts the compound enzyme, which can not only obtain a higher straw cellulose degradation efficiency, but also efficiently decompose the fiber interior, greatly improving the efficiency of straw degradation into monosaccharides. However, it is very easy for monosaccharides to continue to hydrolyze, generate non-target products such as organic acids, and reduce the sugar production efficiency.

[0036] The applicant uses lanthanum chloride to form a complex with aspartic acid, which is then contained in the dendritic structure of ε-polylysine, so that the product has a dendritic macromolecular structure. It not only has excellent adsorption performance for the composite enzyme, making the resulting composite enzyme solution extremely stable, but also has high selectivity for decomposing and preparing monosaccharides and high decomposition activity, which can significantly avoid losses during the treatment process and improve the total yield of monosaccharides. At the same time, it can effectively reduce the dosage of the composite enzyme, so that a higher monosaccharide yield can still be obtained when the dosage of the composite enzyme is relatively low.

[0037] The raw material adopted by the invention is plant straw, which has a wide source and is cheap. Meanwhile, the operation process is simple, the cost is low, the reaction speed is fast and the yield is high, thus providing the possibility for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a comparison chart of the specific surface areas of the straw powder obtained in Example 5, the pretreated straw powder B obtained in Example 5, and the pretreated straw powder B obtained in Comparative Example 1.

[0039] Figure 2 The polysaccharide content comparison chart of corn straw and the residue products after enzymatic hydrolysis obtained in Example 5 and Comparative Examples 1-3 is shown.

[0040] Figure 3 It is a comparison chart of monosaccharide yields of the products obtained in Example 5 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0041] The present invention will be further explained below in conjunction with specific embodiments.

[0042] Example 1

[0043] A method for efficiently degrading plant straw using a microbial composite preparation comprises the following steps:

[0044] S1. Dry and crush the sorghum straw, and pass it through a 40-mesh sieve to obtain straw powder with a moisture content of ≤5%;

[0045] S2, adding 100g urea to 2000g 0.5mol / L sodium hydroxide solution and stirring evenly, adding 1000g straw powder thereto, ultrasonicating at 60°C for 1h, ultrasonic frequency of 10kHz, adding 10g calcium chloride, continuing ultrasonicating for 10min, cooling to -30°C, keeping warm for 10min, heating to 50°C and stirring for 10min, stirring speed of 1000r / min, cooling to room temperature, filtering, washing, and vacuum drying to obtain pretreated straw powder A;

[0046] S3, adding 800g of pretreated straw powder A to 1000g of 1% dilute sulfuric acid solution, stirring at 40°C for 1h, stirring at a speed of 50r / min, cooling to room temperature, filtering, washing once with deionized water, and freeze-drying to obtain pretreated straw powder B;

[0047] S4, add 0.1g of lanthanum chloride to 1000g of water, stir at 40°C for 10min, add 100g of ε-polylysine and 10g of aspartic acid thereto under stirring, stir at 50r / min for 1h, add 100g of complex enzyme thereto and stir evenly to obtain a complex enzyme solution;

[0048] The complex enzyme includes cellulase, xylanase, cellobiase and pectinase; in each gram of the complex enzyme, the enzymatic activity of cellulase is 3000U, the enzymatic activity of xylanase is 2000U, the enzymatic activity of cellobiase is 4000U, and the enzymatic activity of pectinase is 5000U;

[0049] S5. Mix 1000 g of pretreated straw powder B and 300 g of compound enzyme solution, add to 2000 g of acetic acid-sodium acetate buffer solution with a pH value of 4.5, mix evenly, place on a shaker at 40° C. for enzymolysis for 72 h, and centrifuge.

[0050] Example 2

[0051] A method for efficiently degrading plant straw using a microbial composite preparation comprises the following steps:

[0052] S1. Dry and crush the wheat straw, and pass it through an 80-mesh sieve to obtain straw powder with a moisture content of ≤5%;

[0053] S2, adding 300g urea to 4000g 1.5mol / L sodium hydroxide solution and stirring evenly, adding 2000g straw powder thereto, ultrasonicating at 70°C for 2h, ultrasonic frequency of 16kHz, adding 50g calcium chloride, continuing ultrasonicating for 30min, cooling to -50°C, keeping warm for 30min, heating to 60°C and stirring for 20min, stirring speed of 2000r / min, cooling to room temperature, filtering, washing, and vacuum drying to obtain pretreated straw powder A;

[0054] S3, adding 1800g of pretreated straw powder A to 2000g of 2% dilute sulfuric acid solution, stirring at 60°C for 2h, stirring at a speed of 150r / min, cooling to room temperature, filtering, washing with deionized water for 3 times, and freeze-drying to obtain pretreated straw powder B;

[0055] S4, add 1g of lanthanum chloride to 2000g of water, stir at 60°C for 20min, add 1000g of ε-polylysine and 100g of aspartic acid thereto under stirring, stir at 150r / min for 4h, add 200g of complex enzyme thereto and stir evenly to obtain a complex enzyme solution;

[0056] The complex enzyme includes cellulase, xylanase, cellobiase and pectinase; in each gram of the complex enzyme, the enzymatic activity of cellulase is 5000U, the enzymatic activity of xylanase is 4000U, the enzymatic activity of cellobiase is 6000U, and the enzymatic activity of pectinase is 6000U;

[0057] S5. Mix 2000 g of pretreated straw powder B and 600 g of compound enzyme solution, add to 2500 g of acetic acid-sodium acetate buffer solution with a pH value of 5.5, mix evenly, place on a shaker at 46° C. for enzymolysis for 96 hours, and centrifuge.

[0058] Example 3

[0059] A method for efficiently degrading plant straw using a microbial composite preparation comprises the following steps:

[0060] S1. Dry and crush the rice straw, and pass it through a 50-mesh sieve to obtain straw powder with a moisture content of ≤5%;

[0061] S2, adding 250g urea to 2500g sodium hydroxide solution with a concentration of 1.2mol / L and stirring evenly, adding 1200g straw powder thereto, ultrasonicating at 68°C for 80min, ultrasonic frequency of 13kHz, adding 20g calcium chloride, continuing ultrasonicating for 25min, cooling to -35°C, keeping warm for 25min, heating to 53°C and stirring for 18min, stirring speed of 1200r / min, cooling to room temperature, filtering, washing, and vacuum drying to obtain pretreated straw powder A;

[0062] S3, adding 1600g of pretreated straw powder A to 1200g of 1.7% dilute sulfuric acid solution, stirring at 45°C for 100min, stirring at a speed of 80r / min, cooling to room temperature, filtering, washing twice with deionized water, and freeze-drying to obtain pretreated straw powder B;

[0063] S4, add 0.7g lanthanum chloride to 1200g water, stir at 55°C for 12min, add 700g ε-polylysine and 20g aspartic acid thereto under stirring, stir at 120r / min for 2h, add 170g complex enzyme thereto and stir evenly to obtain a complex enzyme solution;

[0064] The complex enzyme includes cellulase, xylanase, cellobiase and pectinase; in each gram of the complex enzyme, the enzymatic activity of cellulase is 3500U, the enzymatic activity of xylanase is 3500U, the enzymatic activity of cellobiase is 4500U, and the enzymatic activity of pectinase is 5700U;

[0065] S5. Mix 1200 g of pretreated straw powder B and 500 g of compound enzyme solution, add to 2000 g of acetic acid-sodium acetate buffer solution with a pH value of 5.5, mix evenly, place on a shaker at 42° C. for enzymolysis for 88 h, and centrifuge.

[0066] Example 4

[0067] A method for efficiently degrading plant straw using a microbial composite preparation comprises the following steps:

[0068] S1. Dry and crush corn stalks, and pass through a 70-mesh sieve to obtain stalk powder with a moisture content of ≤5%;

[0069] S2, adding 150g urea to 3500g 0.8mol / L sodium hydroxide solution and stirring evenly, adding 1800g straw powder thereto, ultrasonicating at 64°C for 100min, ultrasonic frequency of 11kHz, adding 40g calcium chloride, ultrasonicating for 15min, cooling to -45°C, keeping warm for 15min, heating to 57°C and stirring for 12min, stirring speed of 1800r / min, cooling to room temperature, filtering, washing, and vacuum drying to obtain pretreated straw powder A;

[0070] S3, adding 1000g of pretreated straw powder A to 1800g of 1.3% dilute sulfuric acid solution, stirring at 55°C for 80min at a stirring speed of 120r / min, cooling to room temperature, filtering, washing twice with deionized water, and freeze-drying to obtain pretreated straw powder B;

[0071] S4, add 0.3g of lanthanum chloride to 1800g of water, stir at 45°C for 18min, add 300g of ε-polylysine and 80g of aspartic acid thereto under stirring, stir at 80r / min for 3h, add 130g of complex enzyme thereto and stir evenly to obtain a complex enzyme solution;

[0072] The complex enzyme includes cellulase, xylanase, cellobiase and pectinase; in each gram of the complex enzyme, the enzymatic activity of cellulase is 4500U, the enzymatic activity of xylanase is 2500U, the enzymatic activity of cellobiase is 5500U, and the enzymatic activity of pectinase is 5200U;

[0073] S5. Mix 1800 g of pretreated straw powder B and 400 g of compound enzyme solution, add to 2000 g of acetic acid-sodium acetate buffer solution with a pH value of 4.5, mix evenly, place on a shaker at 44° C. for enzymolysis for 80 h, and centrifuge.

[0074] Example 5

[0075] A method for efficiently degrading plant straw using a microbial composite preparation comprises the following steps:

[0076] S1. Dry and crush corn stalks, and pass through a 60-mesh sieve to obtain stalk powder with a moisture content of ≤5%;

[0077] S2, adding 200g urea to 3000g 1mol / L sodium hydroxide solution and stirring evenly, adding 1500g straw powder thereto, ultrasonicating at 66°C for 90min, ultrasonic frequency of 12kHz, adding 30g calcium chloride, ultrasonicating for 20min, cooling to -40°C, keeping warm for 20min, heating to 55°C and stirring for 15min, stirring speed of 1500r / min, cooling to room temperature, filtering, washing, and vacuum drying to obtain pretreated straw powder A;

[0078] S3, adding 1300g of pretreated straw powder A to 1500g of 1.5% dilute sulfuric acid solution, stirring at 50°C for 90min at a stirring speed of 100r / min, cooling to room temperature, filtering, washing twice with deionized water, and freeze-drying to obtain pretreated straw powder B;

[0079] S4, add 0.5g of lanthanum chloride to 1500g of water, stir at 50°C for 15min, add 500g of ε-polylysine and 50g of aspartic acid thereto under stirring, stir at a speed of 100r / min for 2.5h, add 150g of complex enzyme thereto and stir evenly to obtain a complex enzyme solution;

[0080] The complex enzyme includes cellulase, xylanase, cellobiase and pectinase; in each gram of the complex enzyme, the enzymatic activity of cellulase is 4000U, the enzymatic activity of xylanase is 3000U, the enzymatic activity of cellobiase is 5000U, and the enzymatic activity of pectinase is 5500U;

[0081] S5. Mix 1500 g of pretreated straw powder B and 450 g of compound enzyme solution, add to 2500 g of acetic acid-sodium acetate buffer solution with a pH value of 4.8 and mix evenly, place on a shaker at 43° C. for enzymolysis for 84 h, and centrifuge.

[0082] Comparative Example 1

[0083] A method for efficiently degrading plant straw using a microbial composite preparation comprises the following steps:

[0084] S1. Dry and crush corn stalks, and pass through a 60-mesh sieve to obtain stalk powder with a moisture content of ≤5%;

[0085] S2, adding 200g urea to 3000g 1mol / L sodium hydroxide solution and stirring evenly, adding 1500g straw powder thereto, ultrasonicating at 66°C for 90min with an ultrasonic frequency of 12kHz, cooling to room temperature, filtering, washing, and vacuum drying to obtain pretreated straw powder A;

[0086] S3, adding 1300g of pretreated straw powder A to 1500g of 1.5% dilute sulfuric acid solution, stirring at 50°C for 90min at a stirring speed of 100r / min, cooling to room temperature, filtering, washing twice with deionized water, and freeze-drying to obtain pretreated straw powder B;

[0087] S4, add 0.50g of lanthanum chloride to 1500g of water, stir at 50°C for 15min, add 500g of ε-polylysine and 50g of aspartic acid thereto under stirring, stir at a speed of 100r / min for 2.5h, add 150g of complex enzyme thereto and stir evenly to obtain a complex enzyme solution;

[0088] The complex enzyme includes cellulase, xylanase, cellobiase and pectinase; in each gram of the complex enzyme, the enzymatic activity of cellulase is 4000U, the enzymatic activity of xylanase is 3000U, the enzymatic activity of cellobiase is 5000U, and the enzymatic activity of pectinase is 5500U;

[0089] S5. Mix 1500 g of pretreated straw powder B and 450 g of compound enzyme solution, add to 2500 g of acetic acid-sodium acetate buffer solution with a pH value of 4.8 and mix evenly, place on a shaker at 43° C. for enzymolysis for 84 h, and centrifuge.

[0090] Comparative Example 2

[0091] A method for efficiently degrading plant straw using a microbial composite preparation comprises the following steps:

[0092] S1. Dry and crush corn stalks, and pass through a 60-mesh sieve to obtain stalk powder with a moisture content of ≤5%;

[0093] S2, adding 200g urea to 3000g 1mol / L sodium hydroxide solution and stirring evenly, adding 1500g straw powder thereto, ultrasonicating at 66°C for 90min, ultrasonic frequency of 12kHz, adding 30g calcium chloride, ultrasonicating for 20min, cooling to -40°C, keeping warm for 20min, heating to 55°C and stirring for 15min, stirring speed of 1500r / min, cooling to room temperature, filtering, washing, and vacuum drying to obtain pretreated straw powder A;

[0094] S3, adding 1300g of pretreated straw powder A to 1500g of 1.5% dilute sulfuric acid solution, stirring at 50°C for 90min at a stirring speed of 100r / min, cooling to room temperature, filtering, washing twice with deionized water, and freeze-drying to obtain pretreated straw powder B;

[0095] S4. Mix 1500 g of pretreated straw powder B and 450 g of complex enzyme evenly, add to 2500 g of acetic acid-sodium acetate buffer with a pH value of 4.8 and mix evenly, place on a shaker at 43° C. for enzymolysis for 84 hours, and centrifuge.

[0096] The complex enzyme includes cellulase, xylanase, cellobiase and pectinase; in each gram of the complex enzyme, the enzymatic activity of cellulase is 4000U, the enzymatic activity of xylanase is 3000U, the enzymatic activity of cellobiase is 5000U, and the enzymatic activity of pectinase is 5500U.

[0097] Comparative Example 3

[0098] A method for efficiently degrading plant straw using a microbial composite preparation comprises the following steps:

[0099] S1. Dry and crush corn stalks, and pass through a 60-mesh sieve to obtain stalk powder with a moisture content of ≤5%;

[0100] S2, adding 200g urea to 3000g 1mol / L sodium hydroxide solution and stirring evenly, adding 1500g straw powder thereto, ultrasonicating at 66°C for 90min, ultrasonic frequency of 12kHz, adding 30g calcium chloride, ultrasonicating for 20min, cooling to -40°C, keeping warm for 20min, heating to 55°C and stirring for 15min, stirring speed of 1500r / min, cooling to room temperature, filtering, washing, and vacuum drying to obtain pretreated straw powder A;

[0101] S3, adding 1300g of pretreated straw powder A to 1500g of 1.5% dilute sulfuric acid solution, stirring at 50°C for 90min at a stirring speed of 100r / min, cooling to room temperature, filtering, washing twice with deionized water, and freeze-drying to obtain pretreated straw powder B;

[0102] S4, adding 0.5g of lanthanum chloride to 1500g of water, adding 150g of complex enzyme thereto and stirring evenly to obtain a complex enzyme solution;

[0103] The complex enzyme includes cellulase, xylanase, cellobiase and pectinase; in each gram of the complex enzyme, the enzymatic activity of cellulase is 4000U, the enzymatic activity of xylanase is 3000U, the enzymatic activity of cellobiase is 5000U, and the enzymatic activity of pectinase is 5500U;

[0104] S5. Mix 1500 g of pretreated straw powder B and 450 g of compound enzyme solution, add to 2500 g of acetic acid-sodium acetate buffer solution with a pH value of 4.8 and mix evenly, place on a shaker at 43° C. for enzymolysis for 84 h, and centrifuge.

[0105] The specific surface areas of the straw powder obtained in Example 5, the pretreated straw powder B obtained in Example 5, and the pretreated straw powder B obtained in Comparative Example 1 were calculated using the BET nitrogen adsorption-desorption curve.

[0106] like Figure 1 As shown, the pretreated straw powder B obtained in Example 5 effectively increases its specific surface area after being treated with S2 and S3, which is better than the straw powder obtained in Example 5 and the pretreated straw powder B obtained in Comparative Example 1 (P < 0.05), and can significantly reduce the adsorption of lignin on the complex enzyme and reduce the barrier of lignin to the enzyme.

[0107] The polysaccharide content of the corn stalks used and the residue products after enzymatic hydrolysis obtained in Example 5 and Comparative Examples 1-3 was analyzed and then subjected to mass balance treatment. Figure 2 As shown, Example 5 can effectively hydrolyze cellulose and hemicellulose, which is better than Comparative Examples 1-3 (P < 0.05). Comparative Example 3 uses lanthanum chloride directly mixed with the composite enzyme, which will cause the composite enzyme to denature and the hydrolysis ability to drop significantly, which is inferior to Comparative Example 2; but Example 5 uses lanthanum chloride and aspartic acid complexed and assembled in ε-polylysine, which can promote the improvement of the hydrolysis ability of the composite enzyme and accelerate the hydrolysis efficiency.

[0108] The monosaccharide (glucose and xylose) content in the products obtained in Example 5 and Comparative Examples 1-3 (including the filtrates obtained in S2 and S3 and the final enzymatic hydrolysis products) was analyzed by liquid chromatography to calculate the yield. Figure 3 As shown, the monosaccharide yield obtained in Example 5 is the highest, which is better than that in Comparative Examples 1-3 (P < 0.05).

[0109] The applicant believes that the reason for the above results is that the straw powder is added to the sodium hydroxide solution in the present invention, which can effectively weaken the intermolecular binding force of lignin under the synergistic effect of urea, cooperate with the action of calcium chloride and combine with lignin, and cooperate with high and low temperature treatment on the basis of ensuring the stability of the cellulose structure to quickly remove lignin; and the pretreated straw powder A has a large number of holes and fold structures. On the one hand, it is more conducive to the entry of acid at 40-60°C, promoting the hydrolysis of fiber into hemicellulose, that is, it can be hydrolyzed at a lower temperature and is not easy to generate by-products such as furoic acid. On the other hand, its developed void structure is more conducive to increasing the contact area between the subsequent composite enzyme and cellulose or hemicellulose, greatly improving the cellulose degradation efficiency and significantly increasing the monosaccharide yield. The present invention causes the structure of lignin to be broken completely, which not only greatly reduces the adsorption of lignin to composite enzymes, but also reduces the resistance of lignin to enzymes. The present invention adopts composite enzyme compounding, which can not only obtain a higher efficiency of straw cellulose degradation, but also can efficiently decompose the inside of the fiber, greatly improving the efficiency of straw degradation into monosaccharides, but it is very easy for monosaccharides to continue to hydrolyze, generate non-target products such as organic acids, and reduce sugar production efficiency. The applicant uses lanthanum chloride to form a complex with aspartic acid, which is then contained in the dendritic structure of ε-polylysine, so that the product has a dendritic macromolecular structure, which not only has excellent adsorption performance for composite enzymes, but also makes the obtained composite enzyme liquid extremely stable, and has high selectivity for decomposing and preparing monosaccharides, high decomposition activity, which can significantly avoid losses during the treatment process, improve the total yield of monosaccharides, and effectively reduce the dosage of composite enzymes, so that a higher monosaccharide yield can still be obtained when the dosage of composite enzymes is relatively low.

[0110] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for efficiently degrading plant straw using a microbial composite preparation, characterized in that: The steps include: S1, drying plant straw, crushing and sieving to obtain straw powder; S2, adding urea to sodium hydroxide solution and stirring evenly, adding straw powder thereto, ultrasonically treating at 60-70°C for 1-2h, adding calcium chloride and continuing ultrasonically treating for 10-30min, cooling to -30--50°C, keeping warm for 10-30min, heating to 50-60°C and stirring for 10-20min, cooling to room temperature, filtering, washing, and vacuum drying to obtain pretreated straw powder A; S3, adding the pretreated straw powder A to a dilute sulfuric acid solution, stirring at 40-60° C. for 1-2 h, cooling to room temperature, filtering, washing, and freeze-drying to obtain pretreated straw powder B; S4, adding lanthanum chloride to water, stirring at 40-60° C. for 10-20 min, adding ε-polylysine and aspartic acid thereto under stirring, stirring for 1-4 h, adding complex enzyme thereto and stirring evenly to obtain complex enzyme solution; The mass ratio of lanthanum chloride, ε-polylysine, aspartic acid and complex enzyme is 0.001-0.01:1-10:0.1-1:1-2; The complex enzyme includes cellulase, xylanase, cellobiase and pectinase; in each gram of the complex enzyme, the enzymatic activity of the cellulase is 3000-5000U, the enzymatic activity of the xylanase is 2000-4000U, the enzymatic activity of the cellobiase is 4000-6000U, and the enzymatic activity of the pectinase is 5000-6000U; S5. Mix the pretreated straw powder B and the complex enzyme solution evenly, add them into the acetic acid-sodium acetate buffer solution and mix evenly, place them on a shaker at 40-46°C for enzymolysis for 72-96 hours, and centrifuge.

2. The method for efficiently degrading plant straw using a microbial composite preparation according to claim 1, characterized in that: In S1, the moisture content of straw powder is ≤5%.

3. The method for efficiently degrading plant straw using a microbial composite preparation according to claim 1, characterized in that: In S2, the mass ratio of urea, straw powder and calcium chloride is 1-3:10-20:0.1-0.

5.

4. The method for efficiently degrading plant straw using a microbial composite preparation according to claim 1, characterized in that: In S2, the ultrasound frequency is 10-16kHz.

5. The method for efficiently degrading plant straw using a microbial composite preparation according to claim 1, characterized in that: In S2, the concentration of the sodium hydroxide solution is 0.5-1.5 mol / L.

6. The method for efficiently degrading plant straw using a microbial composite preparation according to claim 1, characterized in that: In S3, the mass fraction of the dilute sulfuric acid solution is 1-2%.

7. The method for efficiently degrading plant straw using a microbial composite preparation according to claim 1, characterized in that: In S5, the mass ratio of pretreated straw powder B to complex enzyme solution is 10-20:3-6.

Images